Dr. Story found that the children in two-parent homes had higher reading-test scores than those in one-parent homes. However, the children from two-parent homes had more siblings than those in one-parent homes. What is the confounding variable?

Which of the following animals depends entirely on monocular distance and depth cues?

a. humans c. cats b. deer d. chimpanzees

As an infant, Molly was securely attached to her mother and her father, and this attachment has not changed. When she enters preschool, she is most likely to

a. strenuously resist separating from her parents. b. cling to her teacher in her parents' absence. c. be curious and willing to explore her environment. d. be socially immature.